1. Field of the Invention
The present invention relates to a dry/dew/frost sensor detecting three states (the dry, bedewed, and frosted states) as variations in impedance.
2. Description of the Prior Art
In the use of electrical equipment, moisture control is a difficult problem and thus development of an excellent moisture sensor has been demanded. With certain apparatus, deterioration in characteristics caused by frost as well as that caused by moisture is a serious problem. In the operation of refrigerating equipment, for example, the efficiency is reduced when frost forms on the equipment, and therefore, defrosting becomes necessary. Thus, development of a sensor to detect frosted state has also been demanded.
Hitherto, such a dew sensor, for example, utilizing the variations in resistance resulting from dew formation, and some other types have been developed. Meanwhile, as for frost sensors, such a type as utilizing the change in resonant frequency of a resonating body due to frost formation thereon has been produced. Nothing, however, has been produced to detect both dew and frost, or to discern three states (dry, bedewed, and frosted) with a single sensor. Therefore, in order to detect which of the three states (dry, bedewed, or frosted states) the equipment is in, it has been necessary to use at least two independent sensors, and this has made the equipment complicated.